The purpose of these studies is to apply two-dimensional echocardiograhy to physiologic problems in cardiac surgery. The research has both laboratory and clinical phases. In the laboratory, the validity of the technique of ventricular volume analysis by "biplane" and "single plane" two-dimensional echocardiography will be analyzed. The accuracy of echocardiography for measurement of changes in ventricular volume during systole and estimation of average ventricular wall thickness will be examined. Subsequently, laboratory experiments will analyze the effect of the following parameters on shape and compliance of the canine left ventricle: Thoracotomy, pericardiotomy, temperature change in the range of 15-38 degrees C., volume loading of the right ventricle, mean systolic arterial pressure, and regional ischemia produced by coronary artery ligation. Techniques for light-pen analysis of volume will be demonstrated. In clinical studies, the validity of ventricular volume determination will be calibrated by comparison with biplane angiography and validity of measurements of ejection fraction will be tested against simultaneous measurements by multicrystal scintillation camera. Effects of cardiac surgery on ventricular function and compliance will then be examined preoperatively, intraoperatively, in the immediate postoperative period, and for the first year following surgery. The purpose of the latter studies will be to define a representative profile of changes in physiologic parameters as a result of surgery. These data will then be applied for early definition of long-term prognosis and early detection and departure from the predicted time course of recovery from surgery. This last achievement is an important research goal, for it will facilitate demonstration of effects of improved myocardial preservation on cardiac function.